Some fractures of the radius occur in the part of the bone that is proximate the elbow, called the radial “head”. Radial head fractures are common injuries that may result from an acute elbow injury. Fractures of the radial head are typically treated with a variety of surgical and non-surgical options depending upon the severity of the injury. For example, surgical options for more severe injuries to the radial head can include open reduction with internal fixation (ORIF), radial head resection, hemi-arthroplasty (e.g., radial head arthroplasty), and total arthroplasty (i.e., total elbow replacement).
Radial head arthroplasty involves resecting the fractured and damaged radial head and replacing the natural articulation with an artificial one by use of an implant. The implant articulates with the natural cartilage surface of the capitellum of the distal humerus.
A number of radial head arthroplasty systems are commercially available. For example, the Katalyst™ Bipolar Radial Head System, available from Integra LifeSciences Corporation, headquartered in Plainsboro, N.J., includes the Katalyst™ radial head implants in various sizes as well as associated instrumentation for use in surgery. The radial head implant includes a head portion for articular engagement with a humerus bone, a stem portion for engagement with a radius bone, and a shaft for engagement with the stem portion. The head portion includes an upper surface for engaging the humerus bone. The stem portion has an axial opening for receiving at least a portion of the shaft, and a collar is disposed around the stem portion at a proximal end thereof. An upper portion of the shaft is configured to engage the head portion, while a lower portion of the shaft is elongated and cylindrically shaped for axially fitting into and moving within the axial opening of the stem portion. This commercial product, its variations, associated instrumentation, and methods for using them are described in U.S. Pat. No. 7,740,661, the disclosure of which is incorporated herein by reference in its entirety.
Prior to implantation of a radial head implant, a surgeon will need to select an implant having a size that properly fits the implant site of the particular patient. The Katalyst™ system described above contains trial stems and trial heads the surgeon can assemble and use prior to final implantation to evaluate the fit for selecting the most appropriately sized implant. The trial stems and heads in other radial head systems on the market are also solid pieces. Solid trial pieces are problematic, however, as the surgeon does not have direct visibility of resection levels below the trial piece. This may result in elbow instability problems after radial head arthroplasty.
Accordingly, a need exists for implant sizing tools with enhanced effectiveness for use in orthopedic surgery, including arthroplasty such as radial head arthroplasty.